/Engine/Source/Runtime/Engine/Classes/GameFramework/CharacterMovementComponent.h
Updates Velocity and Acceleration based on the current state, applying the effects of friction and acceleration or deceleration. Does not apply gravity. This is used internally during movement updates. Normally you don't need to call this from outside code, but you might want to use it for custom movement modes.
virtual void CalcVelocity ( float DeltaTime, float Friction, bool bFluid, float BrakingDeceleration )